This table reveals Bonsai care needed per month, around the year, for the Northern hemisphere. These care guidelines are general and mostly applicable for outdoor trees; specific guidelines per species of tree but also per geographical region should have priority. Seasonal Bonsai care January During the winter outdoor trees need to be well protected from freezing temperatures by covering them with insulating material (like layers of leaves, foam, etc.). Control deciduous trees (like the oak) for insects. February Keep checking on insects; outdoor trees will consume little water but watering might be required in the absence of rain. March Some deciduous trees start to grow again, like the ulmus. Most trees can now be left unprotected from freezing temperatures, possible insulating materials can be removed in late March (though depending on your locale climate). Most pine trees can be repotted late march. April Most trees start growing, only a few tree species take more time (like the oak tree). The growth of trees indicates fertilization can be resumed, and trees can now be trained, pruned and repotted. For most trees this is the best time to start wiring; but mind that trees grow rapidly so check on your wiring so it doesn't grow into the bark. May Trees that started growing late (Oak etc) can now be trained and repotted. Fertilization is important now. June Regular pruning of new growth is necessary New growth will result in the trunk and branches growing thicker. July The warmest month of the year; mind to check for watering regularly. August A good moment to repot pine trees. Check your trees for bugs and insects. September Collect seeds from trees; this is the moment! Fertilize outdoor trees for the last time, hardening off their growth and preparing them for the coming winter. October Autumn colors for outdoor trees are spectacular Protect your trees from cold nights. November Keep your trees well protected from freezing temperatures. December Keep checking your tree; they might require watering in the absence of rain.